1. Field of the Invention
The present invention relates to a reduction optical system. More particularly, the present invention relates to a reduction optical system for forming a reduced image of a subject image formed by a replaceable main lens system in, for example, a digital camera or a digital appliance equipped with an image capturing capability that capture an image of a subject with an image sensor, and to an image-taking apparatus provided therewith.
2. Description of Related Art
With the recent spread of personal computers, digital cameras that permit easy capturing of images are becoming increasingly widespread. Thus, with more and more widespread of digital cameras, various specifications have been demanded for a photographing optical system. Since a single-lens reflex camera that records an image on a silver salt film permits lens replacement, the demand described above can be satisfied by applying an interchangeable lens for a single-lens reflex camera to a digital camera. To achieve this, patent documents 1 through 3 each propose a photographing optical system that has a condenser lens arranged near the image surface of the interchangeable lens and that forms in a relay lens system a reduced image of an image formed by the interchangeable lens. Patent document 4 proposes a reduction optical system that achieves reduction without re-imaging an image formed by an interchangeable lens.
[Patent Document 1] Japanese Patent Application Laid-open No. S63-205626
[Patent Document 2] Japanese Patent Application Laid-open No. H7-253537
[Patent Document 3] Japanese Patent Application Laid-open No. H8-114742
[Patent Document 4] Japanese Patent Application Laid-open No. 2000-121932
However, the optical construction proposed in the patent documents 1 through 3 lead to upsizing of an entire photographing optical system due to the configuration such that an image formed by an interchangeable lens is re-imaged. In addition, the optical construction proposed in the patent document 4 suffers from difficulties in achieving satisfactory aberration correction in the added reduction optical system, because the aberration correction has been already completed in the interchangeable lens provided as the main lens system.